Digital broadcasting system and method of processing data

ABSTRACT

A digital broadcasting system and method of processing data are disclosed. The digital broadcasting system includes a transmitting system and a receiving system. The transmitting system comprises a distributed transmission adapter and a plurality of transmitters each being operated as a slave of the distributed transmission adapter, and each sharing the same frequency and transmitting the same signals.

This application claims the benefit of the Korean Patent Application No.10-2006-0131229, filed on Dec. 20, 2006, which is hereby incorporated byreference as if fully set forth herein. This application also claims thebenefit of U.S. Provisional Application No. 60/871,412, filed on Dec.21, 2006, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a digital broadcasting system and amethod of processing data.

2. Discussion of the Related Art

The Vestigial Sideband (VSB) transmission method, which is adopted asthe standard for digital broadcasting in North America and the Republicof Korea, is a system using a single carrier method. Therefore, thereceiving performance of the receiving system may be deteriorated in apoor channel environment. Particularly, since resistance to changes inchannels and noise is more highly required when using portable and/ormobile broadcast receivers, the receiving performance may be even moredeteriorated when transmitting mobile service data by the VSBtransmission method.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a digital broadcastingsystem and a data processing method that substantially obviate one ormore problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a digital broadcastingsystem and a method of processing data that are highly resistant tochannel changes and noise.

Another object of the present invention is to provide a digitalbroadcasting system and a method of processing data that can enhance thereceiving performance of a receiving system by performing additionalencoding on mobile service data and by transmitting the processed datato the receiving system.

A further object of the present invention is to provide a digitalbroadcasting system and a method of processing data that can transmitmobile service data through a single frequency network (SFN).

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, amethod of processing data in a distributed transmission adapter of atransmitting system included in a digital broadcasting system mayinclude performing primary encoding on mobile service data andmultiplexing the primarily encoded mobile service data and main servicedata in packet units, inserting initialization information for trellisencoding module and time and frequency information for a singlefrequency network in a predetermined data packet among the multiplexeddata packets, performing secondary encoding on the processed datapackets and generating initialization data for initializing a memory ofa trellis encoding module at a starting point of a known data sequence,thereby modifying input data of the trellis encoding module, andtransmitting the modified data so as to modify the initialization datafor initializing the memory of the trellis encoding module by usingstatus information of the trellis encoding module, and a identificationsignal for designating an insertion point of a field synchronizationsignal, thereby outputting the generated identification signal to eachtransmitter.

Herein, the step of multiplexing the primarily encoded mobile servicedata and main service data in packet units further includes forming adata group having a plurality of mobile service data packets includedtherein, adjusting a relative position of at least one main service datapacket of a main service data section, the main service data sectionincluding a plurality of main service data packets, and multiplexingmobile service data of the data group and main service data of the mainservice data section to form a burst structure.

In another aspect of the present invention, a method of processing datain a transmitter of a transmitting system included in a digitalbroadcasting system may include recovering trellis code statusinformation, time and frequency information for a single frequencynetwork, and identification information from a predetermined data packetamong a plurality of data packets being transmitted from a distributedtransmission adapter, the identification information designatinginsertion of field synchronization signals, and performing errorcorrection encoding and trellis-encoding processes and inserting fieldsynchronization and segment synchronization signals by using therecovered information, and modulating the processed data so as totransmit the modulated data through an antenna.

In another aspect of the present invention, a distributed transmissionadapter of a transmitting system includes a pre-processor, amultiplexer, an information former, an encoder, and an informationmodifier and synchronization inserter. The pre-processor performsprimary encoding on mobile service data and forms a data group includinga plurality of encoded mobile service data packets. The multiplexermultiplexes and outputs the mobile service data packets of the datagroup outputted from the pre-processor and main service data packets inburst units. The information former inserts initialization informationfor trellis encoder and time and frequency information for a singlefrequency network in a predetermined data packet among the multiplexeddata packets. The encoder performs secondary encoding andtrellis-encoding on the processed data packets outputted from themultiplexer and the information former, and generates initializationdata for initializing a memory of a trellis encoding module at astarting point of a known data sequence, thereby modifying input data ofthe trellis encoding module. Finally, the information modifier andsynchronization inserter transmits the modified data so as to modify theinitialization data for initializing the memory of the trellis encodingmodule by using status information of the trellis encoding module, andgenerates a identification signal for designating an insertion point ofa field synchronization signal, thereby outputting the generatedidentification signal to each transmitter. The distributed transmissionadapter may further include a packet jitter mitigator, which adjusts arelative position of at least one main service data packet of a mainservice data section, wherein the main service data section includes aplurality of main service data packets, and which outputs the at leastone position-adjusted main service data packet to the multiplexer.

In a further aspect of the present invention, a transmitting systemincludes a plurality of transmitters each being operated as a slave of adistributed transmission adapter, and each sharing the same frequencyand transmitting the same signals, wherein each transmitter includes aslave synchronization unit, and a data processor. The slavesynchronization unit recovers trellis code status information, time andfrequency information for a single frequency network, and identificationinformation from a predetermined data packet among a plurality of datapackets being transmitted from the distributed transmission adapter,wherein the identification information designates insertion of fieldsynchronization signal. And, the data processor performs errorcorrection encoding and trellis-encoding processes and inserts fieldsynchronization and segment synchronization signals by using therecovered information, and modulates the processed data so as totransmit the modulated data through an antenna.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a block diagram showing a general structure of adigital broadcasting system according to an embodiment of the presentinvention;

FIG. 2A illustrates a block diagram of a distributed transmissionadapter shown in FIG. 1 according to an embodiment of the presentinvention;

FIG. 2B illustrates a block diagram of a pre-processor shown in FIG. 2Aaccording to an embodiment of the present invention;

FIG. 3 illustrates a block diagram of a distributed transmission adaptershown in FIG. 1 according to another embodiment of the presentinvention;

FIG. 4 illustrates a block diagram of a transmitter shown in FIG. 1according to an embodiment of the present invention;

FIG. 5 illustrates a block diagram of a transmitter shown in FIG. 1according to another embodiment of the present invention;

FIG. 6A to FIG. 6C illustrate exemplary syntax structures of informationrequired for creating a single frequency network (SFN) according to thepresent invention; and

FIG. 7 illustrates a block diagram showing a structure of a receivingsystem according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts. In addition,although the terms used in the present invention are selected fromgenerally known and used terms, some of the terms mentioned in thedescription of the present invention have been selected by the applicantat his or her discretion, the detailed meanings of which are describedin relevant parts of the description herein. Furthermore, it is requiredthat the present invention is understood, not simply by the actual termsused but by the meaning of each term lying within.

In the present invention, the mobile service data may either consist ofdata including information such as program execution files, stockinformation, weather forecast, and so on, or consist of audio/video(A/V) data. Additionally, the known data refer to data already knownbased upon a pre-determined agreement between the transmitting and thereceiving sides. Furthermore, the main service data consist of data thatcan be received from the conventional receiving system, wherein the mainservice data include A/V data. Also, a data service using the mobileservice data may include weather forecast services, traffic informationservices, stock information services, viewer participation quizprograms, real-time polls & surveys, interactive education broadcastprograms, gaming services, services providing information on synopsis,character, background music, and filming sites of soap operas or series,services providing information on past match scores and player profilesand achievements, and services providing information on productinformation and programs classified by service, medium, time, and themeenabling purchase orders to be processed. Herein, the present inventionis not limited only to the services mentioned above.

The present invention relates to a transmission system that can becompatible with the conventional transmission system. Additionally, thetransmission system may also multiplex the main service data and mobileservice data of the same channel, and then, transmit the multiplexeddata. When using the transmitting system according to the presentinvention, the mobile service data may be received while the user is ina mobile state (i.e., traveling). Also, the mobile service data may bereceived with stability despite the noise and diverse distortionoccurring in the channel. Furthermore, the transmitting system accordingto the present invention may perform additional encoding, and insertdata pre-known by both transmitting and receiving sides (i.e., knowndata) and transmit the processed data, thereby enhancing the receivingperformance. The present invention may also mitigate packet jitter whenmultiplexing the main service data and the mobile service data.Furthermore, the present invention enables data to be transmitted byusing a single frequency network (SFN).

FIG. 1 is a conceptual drawing of an exemplary digital broadcast systemapplying the present invention. Referring to FIG. 1, the transmittingsystem includes a distributed transmission adapter (hereinafter referredto as ‘DTxA’) 110, and a plurality of transmitters (or RF transmissionsystems) 121, 122, . . . each operating as a slave in the distributedtransmission adapter (DTxA) 110. Herein, the distributed transmissionadapter (DTxA) 110 and each of the plurality of transmitters 121, 122, .. . is connected to GPS (Global Position System) for external time andfrequency reference.

The distributed transmission adapter (DTxA) 110 is located in studios ofeach broadcast station. And, each of the plurality of transmitters 121,122, . . . is located based upon geographical features or naturalfeatures of the surrounding areas or broadcast regions. The distance andtelecommunication environment between each transmitters 121, 122, . . .and the distributed transmission adapter (DTxA) 110 may differ from oneanother. Herein, the plurality of transmitters 121, 122, . . . sharesthe same frequency in order to use the single frequency network. In thiscase, the plurality of transmitters 121, 122, . . . transmits the samefrequency to the same broadcast signals. For example, the plurality oftransmitters 121, 122, . . . transmits the same frequency for thesignals broadcasted through the Munhwa Broadcasting Corporation (MBC)channel.

Accordingly, in a receiving system according to the present invention, achannel equalizer recognizes the signals transmitted from each of thetransmitters 121, 122, . . . as reflected signals. Thus, the receivingsystem may compensate the received signals, so as to recover thereceived signals back to their initial (or original) state. The datacommunication between the distributed transmission adapter (DTxA) 110and each of the transmitters 121, 122, . . . located in remote sites maybe performed by using a variety of methods. For example, a SynchronousSerial Interface for transport of MPEG-2 data (SMPTE-310M) standard maybe used for the communication of data.

Also, by using the single frequency network, the present invention mayenhance efficiency of frequency usage, thereby effectively broadeningbroadcast coverage. More specifically, since the same broadcast signalsare broadcasted from a plurality of transmitters 121, 122, . . . byusing the same frequency, the present invention can perform efficientusage of frequency. At this point, if the present invention uses the VSBtransmission method, the broadcast system according to the presentinvention should synchronize the following, in order to synchronize eachof the plurality of transmitters 121, 122, . . . .

First of all each of the transmitters 121, 122, . . . should becontrolled so that a carrier frequency of the signals transmitted fromeach transmitters is identical to one another. This is because adifference in frequency among the transmitters 121, 122, . . . may berepresented as a Doppler shift among the received signals, in thereceiving signal, thereby burdening the channel equalizer (i.e.,disturbing the functions of the channel equalizer).

Secondly, a data frame for a VSB mode data transmission is configured of1 odd field synchronization segment (i.e., when all 3 PN63's areidentical to one another) and 312 data segments connected to the oddfield synchronization segment and 1 even field synchronization segment(i.e., when the first and last PN63's are identical to one another, andwhen the second PN63 corresponds to an inversed form), and 312 datasegments connected to the even field synchronization segment. Therefore,the field synchronization segments, which are alternately inversed,should be synchronized, and transport stream (TS) packets used forconfiguring the data frame should be synchronized in each transmitter,respectively.

Finally, the status (or state) of a trellis encoder (including apre-coder) of each transmitter is not initialized at a constant cycleperiod. Therefore, in order to enable the transmitters to output thesame final symbols, the status (or state) of each trellis encoder shouldbe set to be in the same status. More specifically, even if equalsignals are inputted to the trellis encoder of each transmitter, thememory status (or state) of each trellis encoder may differ for eachtransmitter. In this case, each of the transmitters would eventuallyoutput different final symbols.

For this, the distributed transmission adapter (DTxA) 110 according tothe present invention creates an identification signal, which is used byeach transmitter for synchronizing the TS packets and the data frame. Inaddition, the distributed transmission adapter (DTxA) 110 also generatesa distributed transmission packet (DTxP) including trellis encoderstatus information and timing information for frequency transmission.The distributed transmission adapter (DTxA) 110 then transmits theidentification signal and distribution transmission packet (DTxP) toeach of the transmitters 121, 122, . . . . Furthermore, the distributedtransmission adapter (DTxA) 110 transmits VSB mode information andreserved region information of the field synchronization segment to eachof the transmitters 121, 122, . . . through a field rate side channel(FRSC).

Thereafter, each of the transmitters 121, 122, . . . uses theidentification signal to synchronize the data frame to the TS packetthat is being inputted. More specifically, the transmitters may not beable initiate operation simultaneously, or, in case a malfunction orproblem occurs in a particular transmitter, only the correspondingtransmitter may have to re-initiate operation. In this case, aninsertion position of field synchronization signal that have an effecton initialization of trellis encoder, data interleaver, and datarandomizer may use each transmitters 121, 122, . . . differently.Furthermore, even though the same TP data are processed and transmitted,since the status of each data interleaver, data randomizer, and trellisencoder is different from one another, the data being outputted fromeach corresponding transmitter 121, 122, . . . are eventually differentfrom one another as well. Evidently, under such circumstances, thereceiving system is unable to receive data successfully.

Therefore, the identification signal is used as a reference signal forinserting a field synchronization signal at the same point of time ineach of the transmitters 121, 122, . . . . Accordingly, the data at thepoint where signal processing is initiated in each of the transmitters121, 122, . . . may conform with one another.

Additionally, each of the transmitters 121, 122, . . . extracts statusinformation of the trellis encoder (including the pre-coder) in whichthe DTxP is included and accords the status of each trellis encoderswith the pre-determined point of time. For example, each of thetransmitters 121, 122, . . . receives the DTxP and extracts thecorresponding information. Thereafter, prior to having the TP packetinputted to the trellis encoder, wherein the TP packet is subsequent toa very first field synchronization signal that is to be inserted. Thememory status of the trellis encoder is set to be the same as the memorystatus received through the DTxP. Furthermore, each of the transmitters121, 122, . . . extracts time offset information associated with thecorresponding transmitter, thereby adjusting a sending (or transmission)time of an output symbol. More specifically, a global positioning system(GPS) connected to the distributed transmission adapter (DTxA) 110 andeach of the transmitters 121, 122, . . . is used to synchronize the timeand frequency of the distributed transmission adapter (DTxA) 110 andeach of the transmitters 121, 122, . . . .

At this point, the distributed transmission adapter (DTxA) 110 usesexternal reference time information to create time offset informationthat is to be sent to each transmitter 121, 122, . . . . The distributedtransmission adapter (DTxA) 110 also uses an external frequencyreference information in order to accurately match the output TS datarate. Furthermore, each of the transmitters 121, 122, . . . uses theexternal time reference information so as to transmit signals associatedwith the time offset information sent from the distributed transmissionadapter (DTxA) 110. Also, each of the transmitters 121, 122, . . . usesthe external frequency reference information in order to synchronizeeach transmitter 121, 122, . . . with respect to the carrier.

FIG. 2A illustrates a block diagram of a distributed transmissionadapter according to an embodiment of the present invention. Referringto FIG. 2A, the distributed transmission adapter includes a packetjitter mitigator 201, a pre-processor 202, a multiplexer 203, and a DTxPformer 204. Additionally, the distributed transmission adapter furtherincludes a data randomizer 205, a RS encoder/non-systematic RS encoder206, a data interleaver 207, a parity replacer 208, a non-systematic RSencoder 209, a trellis-encoding module 210, a data deinterleaver 211, aRS parity remover 212, a data derandomizer 213, and a DTxP modifier andsync inserter 214.

In the distributed transmission adapter having the above-describedstructure, as shown in FIG. 2A, the main service data are inputted tothe packet jitter mitigator 201, and the mobile service data areinputted to the pre-processor 202. The packet jitter mitigator 201rearranges relative positions of the main service data packets that arebeing inputted. Then, the packet jitter mitigator 201 outputs therepositioned main service data packets to the multiplexer 203. Thepre-processor 202 performs additional encoding so that the mobileservice data can respond more effectively to noise and channelenvironment undergoing frequent changes. Then, the pre-processor 202outputs the processed data to the multiplexer 203 in data group units.The multiplexer 203 then multiplexes the repositioned main service dataand the mobile service data of the data group in TS packet units,thereby outputting the processed data.

FIG. 2B illustrates a block diagram of the pre-processor according to anembodiment of the present invention. Referring to FIG. 2B, thepre-processor includes a data randomizer 251, a RS frame encoder 252, ablock processor 253, a group formatter 254, a data deinterleaver 255,and a packet formatter 256.

The data randomizer 251 receives mobile service data and randomizes thereceived data, thereby outputting the processed mobile service data tothe RS frame encoder 252. At this point, by having the data randomizer251 randomize the mobile service data, a later randomizing process onthe mobile service data performed by a data randomizer 205, which ispositioned in a later block, may be omitted. The randomizer of theconventional system may be identically used as the randomizer forrandomizing the mobile service data. Alternatively, any other type ofrandomizer may also be used for this process.

The RS frame encoder 252 performs at least one of an error correctionencoding process and an error detection encoding process on the inputtedrandomized mobile service data so as to provide robustness on thecorresponding mobile service data. Thus, by providing robustness on themobile service data, a group error that may occur due to a change in thefrequency environment can be scattered, thereby enabling thecorresponding data to respond to the severely vulnerable and frequentlychanging frequency environment. The RS frame encoder 252 may alsoinclude a row permutation process, which permutes mobile service datahaving a predetermined size in row units. Herein, RS encoding is appliedas the error correction encoding process, and cyclic redundancy check(CRC) encoding is applied as the error detection encoding process. Whenperforming RS encoding, parity data that are to be used for errorcorrection are generated. And, when performing CRC encoding, CRC datathat are to be used for error detection are generated.

In this embodiment of the present invention, the RS encoding will beadopting a forward error correction (FEC) method. The FEC corresponds toa technique for compensating errors that occur during the transmissionprocess. The CRC data generated by CRC encoding may be used forindicating whether or not the mobile service data have been damaged bythe errors while being transmitted through the channel. In the presentinvention, a variety of error detection coding methods other than theCRC encoding method may be used, or the error correction coding methodmay be used to enhance the overall error correction ability of thereceiving system.

As described above, the mobile service data encoded by the RS frameencoder 252 are inputted to the block processor 253. The block processor253 then encodes the inputted mobile service data at a coding rate ofG/H (wherein, G is smaller than H (i.e., G<H)) and then outputted to thegroup formatter 254. More specifically, the block processor 113 dividesthe mobile service data being inputted in byte units into bit units.Then, the G number of bits is encoded to H number of bits. Thereafter,the encoded bits are converted back to byte units and then outputted.For example, if 1 bit of the input data is coded to 2 bits andoutputted, then G is equal to 1 and H is equal to 2 (i.e., G=1 and H=2).Alternatively, if 1 bit of the input data is coded to 4 bits andoutputted, then G is equal to 1 and H is equal to 4 (i.e., G=1 and H=4).Hereinafter, the former coding rate will be referred to as a coding rateof ½ (½-rate coding), and the latter coding rate will be referred to asa coding rate of ¼ (¼-rate coding), for simplicity.

Herein, when using the ¼ coding rate, the coding efficiency is greaterthan when using the ½ coding rate, and may, therefore, provide greaterand enhanced error correction ability. For such reason, when it isassumed that the data encoded at a ¼ coding rate in the group formatter254, which is located near the end portion of the system, are allocatedto a region in which the receiving performance may be deteriorated, andthat the data encoded at a ½ coding rate are allocated to a regionhaving excellent receiving performance, the difference in performancemay be reduced. At this point, the block processor 253 may also receiveadditional information data, such as signaling information includingsystem information. Herein, the additional information data may also beprocessed with either ½-rate coding or ¼-rate coding as in the step ofprocessing the enhance data. Thereafter, additional information data,such as signaling information, is also considered the same as the mobileservice data and processed accordingly. The signaling information isinformation required that a receiving system receives and processes dataincluded in a data group. The signaling information may include datagroup information, multiplexing information, burst information, and soon.

Meanwhile, the group formatter 254 inserts mobile service data that areoutputted from the block processor 253 in corresponding regions within adata group, which is configured in accordance with a pre-defined rule.Also, with respect to the data deinterleaving process, each place holderor known data are also inserted in corresponding regions within the datagroup. At this point, the data group may be divided into at least onehierarchical region. Herein, the type of mobile service data beinginserted to each region may vary depending upon the characteristics ofeach hierarchical region. For example, each region may be divided basedupon the receiving performance within the data group.

Herein, the data group is divided into a plurality of different regionsso that each region can be used for different purposes. Morespecifically, a region having less or no interference from the mainservice data may provide a more enhanced (or powerful) receivingperformance as compared to a region having relatively more interferencefrom the main service data. Furthermore, when using a system insertingand transmitting known data into the data group, and when a long knowndata sequence is to be consecutively inserted into the mobile servicedata, a known data sequence having a predetermined length may beconsecutively inserted into a region having no interference from themain service data. Conversely, in case of the regions havinginterference from the main service data, it is difficult toconsecutively insert long known data sequences and to periodicallyinsert the known data into the corresponding regions due to theinterference from the main service data.

In addition, the group formatter 254 also inserts supplemental (orancillary) data, such as signaling information that notifies the overalltransmission information, other than the mobile service data in the datagroup. Also, apart from the encoded mobile service data outputted fromthe block processor 253, the group formatter 254 also inserts MPEGheader place holders, non-systematic RS parity place holders, mainservice data place holders, which are related to data deinterleaving ina later process. Herein, the main service data place holders areinserted because the mobile service data bytes and the main service databytes are alternately mixed with one another based upon the input of thedata deinterleaver. For example, based upon the data outputted after thedata-deinterleaving process, the place holder for the MPEG header may beallocated at the very beginning of each packet.

Furthermore, the group formatter 254 either inserts known data generatedin accordance with a pre-determined method or inserts known data placeholders for inserting the known data in a later process. Additionally,place holders for initializing the trellis encoding module 310 are alsoinserted in the corresponding regions. For example, the initializationdata place holders may be inserted in the beginning of the known datasequence. Herein, the size of the mobile service data that can beinserted in a data group may vary in accordance with the sizes of thetrellis initialization data or known data, MPEG headers, and RS paritydata.

The output of the group formatter 254 is inputted to the datadeinterleaver 255. And, the data deinterleaver 255 deinterleaves data byperforming an inverse process of the data interleaver on the data andplace holders within the data group, which are then outputted to thepacket formatter 256. The packet formatter 256 removes the main servicedata place holders and the RS parity place holders that were allocatedfor the deinterleaving process from the deinterleaved data beinginputted. Then, the packet formatter 256 groups the remaining portionand replaces the 4-byte MPEG header place holder with an MPEG. Also,when the group formatter 254 inserts known data place holders, thepacket formatter 256 may insert actual known data in the known dataplace holders, or may directly output the known data place holderswithout any modification in order to make replacement insertion in alater process. Thereafter, the packet formatter 256 identifies the datawithin the packet-formatted data group, as described above, as a188-byte unit mobile service data packet (i.e., MPEG TS packet), whichis then provided to the multiplexer 203.

The multiplexer 203 multiplexes the mobile service data packet of the188-byte unit outputted from the packet formatter 256 and the mainservice data packet in accordance with a pre-defined multiplexingmethod. Then, the multiplexer 203 outputs the multiplexed data packetsto the DTxP former 204. Herein, the multiplexing method may vary inaccordance with various variables of the system design. One of themultiplexing methods of the multiplexer 203 consists of providing aburst-on section and burst-off section along a time axis, and then,transmitting a plurality of data groups during a burst-on section andtransmitting only the main service data during the burst-off section. Atthis point, main service data may also be transmitted in the burst-onsection. More specifically, a plurality of consecutive mobile servicedata packets is grouped to form a data group. And, a plurality of suchdata groups is mixed with main service data packets so as to create aburst-on section.

In this case, mobile service data and main service data co-exist in aburst-on section, and only the main service data exist in the burst-offsection. Therefore, the main service data section transmitting the mainservice data exist in both the burst-on section and the burst-offsection. At this point, the number of main service data packets includedin the main service data section within the burst-on section and thenumber of main service data packets included in the main service datasection within the burst-off section may be equal to or different fromone another. When the mobile service data are transmitted in burstunits, as described above, a receiving system that only receives themobile service data may turn on the power only during the burst-onsection so as to receive the corresponding data. Also, in this case, thereceiving system may turn off the power during burst-off section,thereby preventing the main service data from being received. Thus, thereceiving system is capable of reducing excessive power consumption.

However, since a data group including mobile service data in-between thedata bytes of the main service data during the packet multiplexingprocess, the shifting of the chronological position (or place) of themain service data packet becomes relative. Also, a system object decoder(i.e., MPEG decoder) for processing the main service data of the digitalbroadcast receiving system, receives and decodes only the main servicedata and recognizes the mobile service data packet as a null datapacket. Therefore, when the system object decoder of the receivingsystem receives a data group including mobile service data and a mainservice data packet that is multiplexed with the data group, a packetjitter occurs.

At this point, since a multiple-level buffer for the video data existsin the system object decoder and the size of the buffer is relativelylarge, the packet jitter generated from the multiplexer 203 does notcause any serious problem in case of the video data. However, since thesize of the buffer for the audio data is relatively small, the packetjitter may cause considerable problem. More specifically, due to thepacket jitter, an overflow or underflow may occur in the buffer for themain service data of the receiving system (e.g., the buffer for theaudio data). Therefore, the packet jitter mitigator 201 re-adjusts therelative position of the main service data packet so that the overflowor underflow does not occur in the system object decoder.

In the present invention, examples of repositioning places for the audiodata packets within the main service data in order to minimize theinfluence on the operations of the audio buffer will be described indetail. The packet jitter mitigator 201 repositions audio packets of themain service data section so that the audio data packets of the mainservice can be positioned as equally and uniformly as possible.

The standard for repositioning the audio data packets in the mainservice data performed by the packet jitter mitigator 201 will now bedescribed. Herein, it is assumed that the packet jitter mitigator 201knows the same multiplexing information as that of the multiplexer 203,which is placed further behind the packet jitter mitigator 201.

Firstly, if one audio data packet exists in the main service datasection (e.g., the main service data section positioned between two datagroups) within the burst-on section, the audio data packet is positionedat the very beginning of the main service data section. Alternatively,if two audio data packets exist in the corresponding data section, oneaudio data packet is positioned at the very beginning and the otheraudio data packet is positioned at the very end of the main service datasection. Further, if more than three audio data packets exist, one audiodata packet is positioned at the very beginning of the main service datasection, another is positioned at the very end of the main service datasection, and the remaining audio data packets are positioned between thefirst and last audio data packets at equal intervals.

Secondly, during the main service data section within the burst-offsection, which is placed immediately before the beginning of a burst-onsection (i.e., during a burst-off section), the audio data packet isplaced at the very end of the main service data section.

Thirdly, during a main service data section within the burst-off sectionsubsequent to the burst-on section, the audio data packet is positionedat the very beginning of the main service data section.

And, finally, the data packets other than audio data packets arepositioned in accordance with the inputted order in vacant spaces (i.e.,spaces that are not designated for the audio data packets). Meanwhile,when the positions of the main service data packets are relativelyre-adjusted, associated program clock reference (PCR) values may also bemodified accordingly. The PCR value corresponds to a time referencevalue for synchronizing the time of the system target decoder. Herein,the PCR value is inserted in a specific region of a TS packet and thentransmitted. In the example of the present invention, the packet jittermitigator 201 also performs the operation of modifying the PCR value.

The output of the packet jitter mitigator 201 is inputted to themultiplexer 203. The multiplexer 203 multiplexes the main service dataoutputted from the packet jitter mitigator 201 and the mobile servicedata outputted from the pre-processor 202, as described above, in burstunits according to a predetermined multiplexing rule. Then, theprocessed data are outputted to the DTxP former 204. The DTxP former 204is connected to the GPS. Herein, when the inputted packet corresponds toan operation and maintenance packet (OMP), then the inputted packet ismodified so as to be configured as a DTxP packet. The OMP is included inthe main service data and inputted to the distributed transmissionadapter 110. The OMP corresponds to a TS-type packet which is used forthe purpose of system operation and maintenance in a MPEG-2 transportsystem. In this embodiment, a packet identifier (PID) of the OMPcorresponds to 0x1FFA. The PID is allocated with 13 bits and indicatedin the header of each MPEG TS packet.

FIG. 6A illustrates a syntax structure of a 184-byte OM packet excludinga 4-byte MPEG TS packet header. The OM packet of FIG. 6A includes anOM_type field and an OM_payload field. In this example, the OM_typefield is allocated with 1-byte, which indicates a type of data structureincluded in the OM_payload field. (In other words, the first byte of the184-byte payload indicates the type of data structure included in theremainder of the payload.) Herein, the OM_payload field is allocatedwith 183 bytes and includes actual data.

When the OM packet is used as the DTxP, the OM_type field has a valueranging from 0x00 to 01F. (In other words, the OM_type field shall beset to a value between 0x00 to 01F so as to indicate the distributedtransmission packet.) If the OM_type field value ranges from 0x00 to01F, the OM_payload field of FIG. 6A may include DTxP informationincluding a DTx_packet( ) syntax structure as shown in FIG. 6B.

Referring to FIG. 6B, a DTxP payload field DTx_packet( ) may include afirst repetition statement being repeated as much as the number oftrellis encoders (e.g., 12 trellis encoders=12 times), asynchronization_time_stamp field, a network_identifier_pattern field, astream_locked_flag field, a packet_number field, a second repetitionstatement being repeated as much as the number of transmitters, and aDTxP_ECC field.

Herein, the first repetition statement includes a trellis_code_statefield. As an example of the present invention, the trellis_code_statefield is allocated with 8 bits and indicates the status information ofeach trellis encoder. The trellis_code_state field carries two copies ofthe three bits corresponding to the status of a pre-coder/trellisencoder pair with added parity data. Herein, one copy is bit-invertedfrom the other. In other words, each trellis encoder includes 3 memoryunits therein. 3 bits are assigned for the status value of the threememories. Among the 3 bits, if the number of ones (1's) corresponds toan even number, then a parity data bit indicating a value of ‘0’ isallocated and added. On the other hand, if the number of ones (1's)corresponds to an odd number, then a parity data bit indicating a valueof ‘1’ is allocated and added. Thereafter, the value for each of the 4bits is inversed, and, accordingly, 4 inversed bits are further added,thereby configuring set of 8 bits allocated to the status information ofthe trellis encoder memory.

In this example, 24 bits are assigned to the synchronization_time_stampfield. Based upon reference signals notifying elapsed time informationof 1 second, which is acquired from the GPS, thesynchronization_time_stamp field indicates the point when an MPEGsynchronization byte of the corresponding DTxP is outputted from thedispersed transmission adapter 110. In other words, thesynchronization_time_stamp (STS) field indicates the elapsed timebetween a 1-second tick of the reference clock and the release from theDTxA of the first bit of the MPEG-2 packet synchronization byte in theheader of the DTxP.

The maximum_delay field is allocated with 24 bits. And, themaximum_delay field indicates a maximum time delay predetermined in thesystem, between an output point of the DTxA 110 and an output point ofthe symbols corresponding to each of the transmitters 121, 122, . . . .In other words, the maximum_delay field indicates the time delay settingin the system between the output time of the DTxA and the time ofemission of the corresponding symbol from each of the transmitters. Morespecifically, the time required for the packets outputted from the DTxA110 to reach each of the transmitters 121, 122, . . . may be differentfrom the time required for data processing the packets in each of thetransmitters 121, 122, . . . . Among the different time delays, thehighest value is notified to each transmitter 121, 122, . . . , therebyenabling all transmitters 121, 122, . . . to transmit signals at thesame point of time.

In this example, 12 bits are assigned to the network_identifier_patternfield. More specifically, the network_identifier_pattern fieldcorresponds to 12 bits of a 24-bit unique (or single) code symbolsequence allocated to each of the transmitters 121, 122, . . . , therebyforming a specific group with a plurality of transmitters equally havingthe same 12 bits. At this point, each of the transmitters 121, 122, . .. may be combined with 12 bits of a tx_address field, which will bedescribed in a later process, thereby forming a seed value of thecombined 24 bits. In other words, the network_identifier_pattern fieldrepresenting the network in which the transmitter is located provides aseed value for 12 of the 24 bits used to set the symbol sequence of aunique code assigned to each transmitter.

The stream_locked_flag field is allocated with 1 bit. Thestream_locked_flag field also indicates whether the transmitteroperating as a slave transmitter locks the symbol clock frequency to aninputted data stream clock frequency, or whether the correspondingtransmitter locks the symbol clock frequency to an identical externalreference frequency. In other words, the stream_locked_flag fieldindicates to a slave transmitter whether it is to lock its symbol clockfrequency to the incoming data stream clock frequency or to lock itssymbol clock frequency to the same external precision referencefrequency used throughout the network.

The packet_number field is allocated with 10 bits and indicates thenumber of MPEG-2 transport stream (TS) packets that have occurred in thestream since the last identification signal to and including the DTxP.

The tx_group_number field is allocated with 8 bits. Herein, thetx_group_number field indicates the first 8 bits of 12-bit addressescorresponding to the specific group of transmitters. In other words, thetx_group_number field that carries the first 8 bits of the 12-bitaddresses of the group of transmitters to which information isindividually addressed in the packet instance.

The second repetition statement is repeated as much as the number oftransmitters. Herein, the second repetition statement includes atx_address field, a tx_identifier_level field, a tx_data_inhibit field,a tx_time_offset field, and a tx_power field.

Herein, the tx_address field is allocated with 12 bits and indicates anaddress of a corresponding transmitter. In other words, the tx_addressfield carries the address of the transmitter to which the followingfields are relevant and which shall be used to seed a portion of the RFwatermark code sequence generator.

In this example, 3 bits are assigned to the tx_identifier_level field,which designates one of the 8 level for transmitting 8 RF watermarksignals of the corresponding transmitter. In other words, thetx_identifier_level field that indicates to which of 8 levels (includingoff) the RF watermark signal of each transmitter shall be set.

The tx_data_inhibit field is allocated with 1 bit. Herein, thetx_data_inhibit field indicates that the tx_data field information isnot encoded by the RF watermark signal. In other words, thetx_data_inhibit field indicates when the tx_data information should notbe encoded into the RF watermark signal.

The tx_time_offset field is allocated with 16 bits. The tx_time_offsetfield indicates a time offset, which corresponds to a difference betweena transmission point defined by the maximum_delay field and an actualtransmission point from each transmitter. In other words, thetx_time_offset field indicates the time offset between a reference timedetermined using maximum_delay and the time of emission of theindividual transmitter to which it is addressed.

The tx_power field is allocated with 12 bits and indicates the powerlevel of the corresponding transmitter.

The DTxP_ECC field is allocated with 160 bits, i.e., 20 bytes, andindicates Reed-Solomon (RS) error correction codes. Herein, the 20 bytesworth of Reed Solomon error correcting code are used to protect theremaining 164 payload bytes of the packet. More specifically, theDTxP_ECC field performs a (164,184)-RS error correction encoding processon 164 bytes of the 184-byte packet configuring the DTxP, wherein the164 bytes carry the remaining information, thereby generating ancarrying 20 bytes of RS parity data.

Referring to FIG. 6A and FIG. 6B, the definitions of the formats willnow be described. More specifically, “bslbf” signifies ‘bit serial,leftmost bit first’, “riuimsbfwp” indicates ‘repeated, inverted,unsigned integer, most significant bit first, with parity’. “riuimsbf”represents ‘repeated, inverted, unsigned integer, most significant bitfirst’. Additionally, “uimsbf” signifies ‘unsigned integer, mostsignificant bit first’, and “uipfmsbf” means ‘unsigned integer plusfraction, most significant bit first’. Furthermore, “tcimsbf” represents‘twos complement integer, most significant bit first’.

As shown in FIG. 6B, the DTxP payload includes status information ofeach of the 12 trellis encoders, diverse time information, time offsetor power level information corresponding to each transmitter, and so on.Additionally, a 20-byte parity is also included in the DTxP payload, the20-byte parity having the above-mentioned information RS-coded therein.At this point, the DTxP former 204 inserts a trellis_code_state fieldvalue and a RS parity value, among the DTxP information of FIG. 6B, asdefault values. The remaining information uses the reference time andfrequency information of the GPS so as to insert diverse data types,which configure the single frequency network. The output of the DTxPformer 204 is inputted to the data randomizer 205.

If the inputted data correspond to the main service data packet, thedata randomizer 205 performs the same randomizing process as that of theconventional randomizer. More specifically, the synchronization bytewithin the main service data packet is deleted. Then, the remaining 187data bytes are randomized by performing a bitwise exclusive OR (XOR)operation on a pseudo random byte generated from the data randomizer205. Thereafter, the randomized data are outputted to the RSencoder/non-systematic RS encoder 206.

On the other hand, if the inputted data correspond to the mobile servicedata packet, the data randomizer 205 deletes the synchronization bytefrom the 4-byte MPEG header included in the mobile service data packetand, then, performs the randomizing process only on the remaining 3 databytes of the MPEG header. Thereafter, the randomized data bytes areoutputted to the RS encoder/non-systematic RS encoder 206. Additionally,the randomizing process is not performed on the remaining portion of themobile service data excluding the MPEG header. In other words, theremaining portion of the mobile service data packet is directlyoutputted to the RS encoder/non-systematic RS encoder 206 without beingrandomized. This is because a randomizing process has already beenperformed on the mobile service data in the data randomizer 251. Also,the data randomizer 205 may or may not perform a randomizing process onthe known data (or known data place holders) and the initialization dataplace holders included in the mobile service data packet. Further, thedata randomizer 205 may continue to generate pseudo random bytes even inthe mobile service sections.

The RS encoder/non-systematic RS encoder 206 performs an RS-codingprocess on the data being randomized by the data randomizer 205 or onthe data bypassing the data randomizer 205, so as to add 20 bytes of RSparity data. Thereafter, the processed data is outputted to the datainterleaver 207. Herein, if the inputted data correspond to the mainservice data packet, the RS encoder/non-systematic RS encoder 206performs the same systematic RS-encoding process as that of theconventional system, thereby adding the 20-byte RS parity data at theend of the 187-byte data. Alternatively, if the inputted data correspondto the mobile service data packet, the RS encoder/non-systematic RSencoder 206 performs a non-systematic RS-encoding process. At thispoint, the 20-byte RS parity data obtained from the non-systematicRS-coding process is inserted in a pre-decided parity byte place withinthe mobile service data packet.

The data interleaver 207 corresponds to a byte unit convolutionalinterleaver. The output of the data interleaver 207 is inputted to theparity replacer 208 and to the non-systematic RS encoder 209. Meanwhile,a process of initializing a memory within the trellis encoding module210 is primarily required in order to decide the output data of thetrellis encoding module 210, which is located after the parity replacer208, as the known data pre-defined according to an agreement between thereceiving system and the transmitting system. More specifically, thememory of the trellis encoding module 210 should first be initializedbefore the inputted known data sequence is trellis-encoded.

At this point, the beginning portion of the known data sequence that isinputted corresponds to the initialization data place holder and not tothe actual known data. Therefore, the process of generatinginitialization data and replacing the initialization data place holderof the corresponding memory with the generated initialization data arerequired to be performed immediately before the inputted known datasequence is trellis-encoded.

Additionally, a value of the trellis memory initialization data isdecided and generated based upon a memory status of the trellis encodingmodule 210. Further, due to the newly replaced initialization data, aprocess of newly calculating the RS parity and replacing the RS parity,which is outputted from the data interleaver 207, with the newlycalculated RS parity is required. Therefore, the non-systematic RSencoder 209 inputs the mobile service data packet including theinitialization data place holders, which are to be replaced with theactual initialization data, from the data interleaver 207 and alsoinputs the initialization data from the trellis encoding module 210.

Among the inputted mobile service data packet, the initialization dataplace holders are replaced with the initialization data, and the RSparity data that are added to the mobile service data packet areremoved. Thereafter, a new non-systematic RS parity is calculated andthen outputted to the parity replacer 208. Accordingly, the parityreplacer 208 selects the output of the data interleaver 207 as the datawithin the mobile service data packet, and the parity replacer 208selects the output of the non-systematic RS encoder 209 as the RS paritydata. Then, the selected data are outputted to the trellis encodingmodule 210.

Meanwhile, if the main service data packet is inputted or if the mobileservice data packet, which does not include any initialization dataplace holders, is inputted, the parity replacer 208 selects the data andRS parity that are outputted from the data interleaver 207. Then, theparity replacer 208 directly outputs the selected data to the trellisencoding module 210 without any modification.

As described above, the trellis encoding module 210 performstrellis-encoding and modifies the input data of the trellis encodingmodule 210 so that a memory of the trellis encoding module 210 can beinitialized to a desired state at the starting point of a known datasequence. Thereafter, the trellis encoding module 210 outputs themodified input data (i.e., the trellis memory initialization data) tothe non-systematic RS encoder 209 and to the data deinterleaver 211.More specifically, the trellis encoding module 210 does not output anytrellis-encoded output symbols. Instead, the trellis encoding module 210outputs the modified input data of the trellis encoding module 210.Additionally, the trellis encoding module 210 outputs memory statusinformation of the trellis encoder to the DTxP modifier and syncinserter 214.

The data deinterleaver 211 receives the remaining data excluding themodified data from the parity replacer 208. Then, the data deinterleaver211 performs an inverse process of the data interleaver 207 on thereceived data and outputs the processed data to the RS parity remover212. Without determining whether the received data correspond to mainservice data or mobile service data, the RS parity remover 212 removesthe last 20 bytes from the 207-byte RS-encoded data packet. Thereafter,the RS parity remover 212 outputs the parity-removed data to the dataderandomizer 213. The data derandomizer 213 derandomizes the received187 data bytes without determining whether the received RS-encoded datapacket having the last 20 bytes removed by the RS parity remover 212correspond to the main service data or the mobile service data.Thereafter, the data derandomizer 213 outputs the derandomized data tothe DTxP modifier and sync inserter 214.

The DTxP modifier and sync inserter 214 adds a MPEG synchronization byteto the output data of the data derandomizer 213, which is being inputtedin 187-byte packet units, thereby forming a 188-byte unit TS packet. Atthis point, the transmitter generates an identification signal at apredetermined cycle period of one data packet, so that the data packetsand the TS packets can be synchronized. For example, the identificationsignal may be generated after each set of 312 data packets or after eachset of 624 data packets. At this point, when a identification signal isgenerated for each set of 312 data packets, the identification signalmay respectively designate insertion positions of an odd fieldsynchronization signal and an even field synchronization signal. In thiscase, the identification signal values for each field may be identicalto one another or different from one another.

Conversely, when a identification signal is generated for each set of624 data packets, the identification signal may designate an insertionpositions for any one of the odd field synchronization signal and theeven field synchronization signal. For example, when it is assumed thatthe identification signal is generated for each set of 624 data packetsand that the identification signal designates the insertion position ofthe odd field synchronization signal, the even field synchronizationsignal is inserted after 312 data segments from the odd fieldsynchronization signal. Herein, the counting of the data segments beginsfrom the data segment subsequent to the odd field synchronizationsignal. The data packet may correspond to any one of the main servicedata packet and the mobile service data.

The identification signal values may indicate values pre-decided basedupon an agreement between the transmitting system and the receivingsystem. For example, the synchronization byte values may be modified soas to be used as the identification signals. More specifically, thesynchronization byte values may be inversed for each bit so as to beused as the identification signal. Alternatively, the synchronizationbyte values may be partially inversed so as to be used as theidentification signals. When it is assumed that the synchronization bytevalues are inversed for each bit so as to be used as the identificationsignals, this indicates that a synchronization byte (0x47) of the MPEG-2TS packet is inversed for each bit at a predetermined data packet cycle(e.g., a cycle of 312 data packets or 624 data packets). In other words,if the synchronization byte is 0x47, the identification signal may be0xB8.

At this point, the inversion of the MPEG synchronization byte should besynchronized with the operation of the multiplexer 203 shown in FIG. 2A.This is because the mobile service data packet is multiplexed with themain service data packet at a fixed position based upon a fieldsynchronization signal. Therefore, the generation of the identificationsignal is also related to the operation of the multiplexer 203 shown inFIG. 2A. The DTxP modifier and sync inserter 214 searches for a DTxPamong the data packets having an MPEG synchronization byte insertedtherein. The DTxP may be searched by using a variety of methods. Amethod of searching the DTxP by using a PID value will be given as anexemplary method according to an embodiment of the present invention.

If the inputted data packet is a DTxP, the DTxP modifier and syncinserter 214 inserts status information (i.e., a memory status) of atrellis encoder at a predetermined point, the status information beinginputted from the trellis encoding module 210, to a trellis_code_statefield shown in FIG. 6B. The DTxP modifier and sync inserter 214 then(N,K)(N=184,K=164)-RS-encodes the inserted memory status, therebyinserting 20 bytes of parity data to a DTxP_ECC field of shown in FIG.6B. Meanwhile in the VSB mode broadcasting system, 24 bits of VSB modedata and 92 bits of reserved data are transmitted to the fieldsynchronization segment. At this point, the DTxP modifier and syncinserter 214 transmits data shown in FIG. 6C through the FRSC, so as toenable each transmitter to transmit the same VSB mode data and reserveddata.

FIG. 6C illustrates an exemplary syntax structure of a Field Rate SideChannel( ). Herein, the FRSC data may include a VSB_mode_data field, adfs_reserved_data field, and a side_channel_ECC field. Morespecifically, the VSB_mode_data field is allocated with 24 bits andtransmits VSB mode data. The dfs_reserved_data field is allocated with92 bits and transmits reserved data. And, the side_channel_ECC field isallocated with 160 bits and transmits 20 bytes of RS parity data.Herein, a reserved field allocated with 36 bits may be further includedbetween the dfs_reserved_data field and the side_channel_ECC field. Atthis point, the VSB_mode_data field, the dfs_reserved_data field, andthe reserved field collectively consist of 19 bytes.

The DTxP modifier and sync inserter 214 performs(N,K)(N=39,K=19)-RS-encoding on the 19 bytes so as to generate 20 bytesof parity data, which are then inserted to the side_channel_ECC field.More specifically, the DTxP modifier and sync inserter 214 RS-encodesthe 19-byte information so as to create (or generate) a total of 39bytes (i.e., 312 bits). The DTxP modifier and sync inserter 214transmits the FRSC data, as described in FIG. 6C, to each of thetransmitters 121, 122, . . . .

Herein, the FRSC data may be transmitted by using a variety of methods.In the example of the present invention, the FRSC data are inserted inthe transport_error_indicator flag field of the inputted TS packetheader, thereby transmitted to each of the transmitters 121, 122, . . .. More specifically, the 312-bit FRSC data are transmitted through the1-bit transport_error_indicator flag field, which is included in the TSpacket header. At this point, since one data field transmits 312 TSpackets, one set of 312-bit FRSC data is transmitted to each of thetransmitters 121, 122, . . . for each data field.

The output of the DTxP modifier and sync inserter 214 is inputted toeach transmitter (or DTV transmitter) as the final output of thedistributed transmission adapter (DTxA). According to another embodimentof the present invention, the FRSC data may be inserted by the DTxPformer 204 instead of the DTxP modifier and sync inserter 214.

FIG. 3 illustrates a distributed transmission adapter (DTxA) of FIG. 2Aaccording to another embodiment of the present invention. The differencebetween the distributed transmission adapter (DTxA) of FIG. 2A and thatshown in FIG. 3 is the RS parity remover 312 and the data derandomizer313. More specifically, when the inputted data corresponds to the mainservice data, the RS parity remover 312 shown in FIG. 3 removes the last20 bytes of the inputted 207 data bytes. Alternatively, when theinputted data corresponds to the mobile service data, the RS parityremover 312 removes 20 bytes of non-systematic RS parity data existingin pre-decided positions within the received 207 data bytes.

Furthermore, referring to FIG. 3, the data derandomizer 313 derandomizesthe main service data, and internally generates pseudo random bytewithin respect to the mobile service data, thereby enabling the inputdata to directly bypass the DTxP modifier and sync inserter 314 withoutmodification. Since the configuration and operation of the blocks shownin FIG. 3 are identical to those shown in FIG. 2A, with the exception ofthe RS parity remover 312 and the data derandomizer 313, a detaileddescription of the same will be omitted for simplicity.

FIG. 4 illustrates a block diagram of a transmitter (or DTV transmitter)operating as a slave of the distributed transmission adapter (DTxA) ofFIG. 2A according to an embodiment of the present invention. Thetransmitter of FIG. 4 may include a slave synchronizer 400 and a signalprocessing and RS up-converting unit 410. Herein, the signal processingand RS up-converting unit 410 may either have the same structure as thatincluded in the conventional transmitter, or have the same structure ofanother disclosed transmitter. In the embodiment of the presentinvention, the signal processing and RS up-converting unit 410 using theconventional transmitter will be described. In this case, the signalprocessing and RS up-converting unit 410 includes a data randomizer 411,a RS encoder 412, a data interleaver 413, a trellis encoder 414, amultiplexer 415, a pilot inserter 416, a modulator 417, and a RSup-converter 418.

The slave synchronizer 400 of FIG. 4 performs an operation enabling thesignal processing and RS up-converting unit 410 to operate a slave ofthe distributed transmission adapter 110 in order to embody a singlefrequency network. The slave synchronizer 400 receives the TS packettransmitted from the distributed transmission adapter 110, so as todetect the identification signal. For example, if the identificationsignal is inputted once for each set of 624 data packets, and that theMPEG synchronization byte values are inversed for each bit so as to beused as the identification signals, the slave synchronizer 400 detectsthe MPEG synchronization bytes inverted for each set of 624 datapackets, thereby recovering the identification signal. Thus, the signalprocessing and RS up-converting unit 410 may synchronize the inputted TSpackets and the data frame. In other words, by having the data frameinsert the field synchronization based upon the identification signal,the data packets and data frame may be synchronized.

Meanwhile, the slave synchronizer 400 filters the PID so as to detectthe DTxP. Then, the slave synchronizer 400 performs(N,K)(N=184,K=164)-RS decoding on the detected DTxP, thereby correctingthe errors that may occur in the channels between the distributedtransmission adapter 110 and the transmitters 121, 122, . . . .Subsequently, the trellis code status information is extracted from theRS-decoded DTxP, which is then provided to the signal processing and RSup-converting unit 410. Thereafter, the signal processing and RSup-converting unit 410 uses the RS-decoded DTxP to set the memory statusof the trellis encoder 414 to a corresponding status at a pre-decidedpoint.

In other words, each of the transmitters 121, 122, . . . receives a DTxPso as to detect trellis code status information. Then, each of thetransmitters 121, 122, . . . initializes the memory of the trellisencoder included in the corresponding transmitter to the detectedtrellis encoder status value of the distributed transmission adapter ata pre-decided point. Thus, the status of the trellis encoder included ineach transmitter may be synchronized at a fixed point, thereby enablingthe final symbol output of each transmitter to be identical to oneanother.

Additionally, the slave synchronizer 400 uses the timing controlinformation extracted from the DTxP and the reference time and frequencyof the GPS so as to accurately control the transmission time andfrequency of the final signal outputted from the signal processing andRS up-converting unit 410. At this point, with the exception of theDTxP, the slave synchronizer 400 internally performs adequate bufferingon the remaining portion of the inputted TS packet. Thereafter, theprocessed (or buffered) data are directly passed on the data randomizer411 of the signal processing and RS up-converting unit 410 withoutmodification.

Conversely, with respect to the DTxP, the trellis code status and20-byte RS parity are recovered to default values, which are thenprovided to the signal processing and RS up-converting unit 410. This isbecause the trellis code status and 20-byte RS parity, which aretransmitted from the distributed transmission adapter, correspond toinformation inserted to the signal processing and RS up-converting unit410 and not to the DTxP former 204 of the distributed transmissionadapter. Therefore, the slave synchronizer 400 inserts the trellis codestatus and RS parity, which are used as default values in the DTxPformer 204 of the distributed transmission adapter, to thetrellis_code_state field and the DTxP_ECC field. Thereafter, the slavesynchronizer 400 transmits the processed data to the signal processingand RS up-converting unit 410.

Furthermore, the slave synchronizer 400 recovers the VSB mode andreserved bit values included in the field synchronization segment fromthe FRSC data of the TS packet header. Then, the slave synchronizer 400provides the recovered VSB mode and reserved bit values to the signalprocessing and RS up-converting unit 410, thereby allowing the recoveredinformation to be transmitted to the field synchronization segment.

At this point, if the FRSC data were inserted in the DTxP modifier andsync inserter 214 of the distributed transmission adapter, the slavesynchronizer 400 extracts the FRSC data from thetransport_error_indicator flag field within 312 TS packets.Subsequently, the FRSC data are set to a default value (e.g., ‘0’)within the transport_error_indicator flag field, which are thenoutputted to the signal processing and RS up-converting unit 410.Herein, the default value corresponds to a value pre-decided by the DTxPformer 204 of the distributed transmission adapter for setting thetransport_error_indicator flag field.

The signal processing and RS up-converting unit 410 of FIG. 4 receivesthe output of the slave synchronizer 400, so as to perform the samesignal processing steps as the conventional transmitting system.Thereafter, the signal processing and RS up-converting unit 410up-converts the processed signal to a RF band signal, therebytransmitting the corresponding frequency. More specifically, the datarandomizer 411 randomizes the data inputted from the slave synchronizer400, without determining whether the received data corresponds to themain service data or the mobile service data. Then, the slavesynchronizer 400 outputs the randomized data to the data interleaver413.

The data interleaver 413 interleaves the inputted data and outputs theinterleaved data to the trellis encoder 414. The trellis encoder 414extracts the trellis code status outputted from the slave synchronizer400 so as to set up the memory of the trellis encoder to a desiredstatus corresponding to a pre-decided point. The data trellis-encoded bythe trellis encoder 414 are inputted to the multiplexer 415. Themultiplexer 415 refers to the identification signal provided by theslave synchronizer 400 and inserts field synchronization and segmentsynchronization signals to the data outputted from the trellis encoder414. Then, the processed data are outputted to the pilot inserter 416.Subsequently, the pilot inserter 416 outputs the pilot-inserted data tothe modulator 417 so as to be modulated. Thereafter, the modulated dataare transmitted to each receiving system through the RF up-converter418.

FIG. 5 illustrates a block diagram of a transmitter corresponding to thedistributed transmission adapter of FIG. 3 according to an embodiment ofthe present invention. The role and operation of the slave synchronizer500 shown in FIG. 5 are identical to those of the slave synchronizer 400shown in FIG. 4. However, the operations of the data randomizer 511 andthe RS encoder/non-systematic RS encoder 512 included in the signalprocessing and RS up-converting unit 510 of FIG. 5 are different fromthose of the signal processing and RS up-converting unit 410 shown inFIG. 4.

More specifically, if the inputted data corresponds to the main servicedata, the data randomizer 511 deletes the synchronization byte withinthe inputted main service data. Then, the remaining 187 data byte israndomized by performing a bitwise exclusive OR (XOR) operation on apseudo random byte generated from the data randomizer 511. Thereafter,the randomized data are outputted to the RS encoder/non-systematic RSencoder 512. The RS encoder/non-systematic RS encoder 512 performs anRS-encoding process on the data being randomized by the data randomizer511 or on the data bypassing the data randomizer 511, so as to add 20bytes of RS parity data. Thereafter, the processed data are outputted tothe data interleaver 513.

Herein, if the inputted data corresponds to the main service datapacket, the RS encoder/non-systematic RS encoder 512 performs the samesystematic RS-encoding process as that of the conventional system,thereby adding the 20-byte RS parity data at the end of the 187-bytedata. Alternatively, if the inputted data corresponds to the mobileservice data packet, the RS encoder/non-systematic RS encoder 512performs a non-systematic RS-coding process. At this point, the 20-byteRS parity data obtained from the non-systematic RS-coding process isinserted in a pre-decided parity byte place within the mobile servicedata packet. Furthermore, since the blocks subsequent to the signalprocessing and RS up-converting unit 510 of the data interleaver 513 ofFIG. 5 are identical to those shown in FIG. 4, a detailed description ofthe same will be omitted for simplicity.

FIG. 7 illustrates a block diagram showing a structure of a receivingsystem according to the present invention. The receiving system of FIG.7 uses known data information, which is inserted in the mobile servicedata section and, then, transmitted by the transmitting system, so as toperform carrier recovery, timing recovery, frame synchronizationrecovery, and channel equalization, thereby enhancing the receivingperformance.

Referring to FIG. 7, the receiving system includes a tuner 701, ademodulator 702, an equalizer 703, a known sequence detector 704, ablock decoder 705, a data deformatter 706, a RS frame decoder 707, adata derandomizer 708, a data deinterleaver 709, a RS decoder 710, and adata derandomizer 711. Herein, for simplicity of the description of thepresent invention, the data deformatter 706, the RS frame decoder 707,and the data derandomizer 708 will be collectively referred to as amobile service data processing unit. And, the data deinterleaver 709,the RS decoder 710, and the data derandomizer 711 will be collectivelyreferred to as a main service data processing unit.

More specifically, the tuner 701 tunes a frequency of a particularchannel and down-converts the tuned frequency to an intermediatefrequency (IF) signal. Then, the tuner 701 outputs the down-converted IFsignal to the demodulator 702 and the known sequence detector 704. Thedemodulator 702 performs self gain control, carrier recovery, and timingrecovery processes on the inputted passband IF signal, thereby modifyingthe IF signal to a baseband signal. Then, the demodulator 702 outputsthe newly created baseband signal to the equalizer 703 and the knownsequence detector 704. The equalizer 703 compensates the distortion ofthe channel included in the demodulated signal and then outputs theerror-compensated signal to the block decoder 705.

At this point, the known sequence detector 704 detects the knownsequence place inserted by the transmitting end from the input/outputdata of the demodulator 702 (i.e., the data prior to the demodulationprocess or the data after the demodulation process). Thereafter, theplace information along with the symbol sequence of the known data,which are generated from the detected place, is outputted to thedemodulator 702 and the equalizer 703. Also, the known sequence detector704 outputs a set of information to the block decoder 705. This set ofinformation is used to allow the block decoder 705 of the receivingsystem to identify the mobile service data that are processed withadditional encoding from the transmitting system and the main servicedata that are not processed with additional encoding. In addition,although the connection status is not shown in FIG. 7, the informationdetected from the known sequence detector 704 may be used throughout theentire receiving system and may also be used in the data deformatter 706and the RS frame decoder 707. The demodulator 702 uses the known datasymbol sequence during the timing and/or carrier recovery, therebyenhancing the demodulating performance. Similarly, the equalizer 703uses the known data so as to enhance the equalizing performance.Moreover, the decoding result of the block decoder 705 may be fed-backto the equalizer 703, thereby enhancing the equalizing performance.

Meanwhile, if the data being inputted to the block decoder 705, afterbeing channel-equalized by the equalizer 703, correspond to the mobileservice data having additional encoding and trellis encoding performedthereon by the transmitting system, trellis decoding and additionaldecoding processes are performed on the inputted data as inverseprocesses of the transmitting system. Alternatively, if the data beinginputted to the block decoder 705 correspond to the main service datahaving only trellis encoding performed thereon, and not the additionalencoding, only the trellis decoding process is performed on the inputteddata as the inverse process of the transmitting system. The data groupdecoded by the block decoder 705 is outputted to the data deformatter706, and the main service data are outputted to the data deinterleaver709.

More specifically, if the inputted data correspond to the main servicedata, the block decoder 705 performs Viterbi decoding on the inputteddata so as to output a hard decision value or to perform a hard-decisionon a soft decision value, thereby outputting the result. Meanwhile, ifthe inputted data correspond to the mobile service data, the blockdecoder 705 outputs a hard decision value or a soft decision value withrespect to the inputted mobile service data. In other words, if theinputted data correspond to the mobile service data, the block decoder705 performs a decoding process on the data encoded by the blockprocessor and trellis encoding module of the transmitting system.

At this point, the RS frame encoder of the pre-processor included in thetransmitting system may be viewed as an external code. And, the blockprocessor and the trellis encoder may be viewed as an internal code. Inorder to maximize the performance of the external code when decodingsuch concatenated codes, the decoder of the internal code should outputa soft decision value. Therefore, the block decoder 705 may output ahard decision value on the mobile service data. However, when required,it may be more preferable for the block decoder 705 to output a softdecision value.

Meanwhile, the data deinterleaver 709, the RS decoder 710, and the dataderandomizer 711 are blocks required for receiving the main servicedata. Therefore, the above-mentioned blocks may be omitted from thestructure of a receiving system that only receives the mobile servicedata. The data deinterleaver 709 performs an inverse process of the datainterleaver included in the transmitting system. In other words, thedata deinterleaver 709 deinterleaves the main service data outputtedfrom the block decoder 705 and outputs the deinterleaved main servicedata to the RS decoder 710.

The RS decoder 710 performs a systematic RS decoding process on thedeinterleaved data and outputs the processed data to the dataderandomizer 711. The data derandomizer 711 receives the output of theRS decoder 710 and generates a pseudo random data byte identical to thatof the randomizer included in the transmitting system. Thereafter, thedata derandomizer 711 performs a bitwise exclusive OR (XOR) operation onthe generated pseudo random data byte, thereby inserting the MPEGsynchronization bytes to the beginning of each packet so as to outputthe data in 188-byte main service data packet units.

Meanwhile, the data being outputted from the block decoder 705 to thedata deformatter 706 are inputted in the form of a data group. At thispoint, the data deformatter 706 already knows the structure of the datathat are to be inputted and is, therefore, capable of identifying thesignaling information, which includes the system information, and themobile service data from the data group. Thereafter, the datadeformatter 706 outputs the identified signaling information to a blockfor processing signaling information (not shown) and outputs theidentified mobile service data to the RS frame decoder 707. At thispoint, the data deformatter 706 removes the known data, trellisinitialization data, and MPEG header, which were inserted in the mainservice data and data group, and also removes the RS parity, which wasadded by the RS encoder/non-systematic RS encoder or non-systematic RSencoder of the transmitting system, from the corresponding data.Thereafter, the processed data are outputted to the RS frame decoder707. More specifically, the RS frame decoder 707 receives only the RSencoded and/or CRC encoded mobile service data that are transmitted fromthe data deformatter 706.

The RS frame decoder 707 performs an inverse process of the RS frameencoder included in the transmitting system so as to correct the errorwithin the RS frame. Then, the RS frame decoder 707 adds the 1-byte MPEGsynchronization service data packet, which had been removed during theRS frame encoding process, to the error-corrected mobile service datapacket. Thereafter, the processed data packet is outputted to the dataderandomizer 708. The data derandomizer 708 performs a derandomizingprocess, which corresponds to the inverse process of the randomizerincluded in the transmitting system, on the received mobile servicedata. Thereafter, the derandomized data are outputted, thereby obtainingthe mobile service data transmitted from the transmitting system.

As described above, the present invention has the following advantages.More specifically, the present invention is robust against (or resistantto) any error that may occur when transmitting mobile service datathrough a channel. And, the present invention is also highly compatibleto the conventional system. Moreover, the present invention may alsoreceive the mobile service data without any error even in channelshaving severe ghost effect and noise.

Additionally, information, such as identification signals fordesignating insertion points (or positions) of field synchronizationsignals in a distributed transmission adapter, information for matchingtrellis encoder states of each transmitter to coincide at a pre-decidedpoint, timing offset information, and so on, are generated andtransmitted to each transmitter operating as slaves of the distributedtransmission adapter. Thus, the conventional transmitter structure maybe used without modification. And, at the same time, mobile service datamay be transmitted to a single frequency network. Furthermore, thepresent invention is even more effective when applied to mobile andportable receivers, which are also liable to a frequent change inchannel and which require protection (or resistance) against intensenoise.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A method of processing digital broadcast data in a digital broadcastreceiver, the method comprising: receiving a digital broadcast signalcomprising main service data, mobile service data, and known datasequences, wherein the digital broadcast signal is processed in adigital broadcast transmitter by: randomizing mobile service data in afirst randomizer, performing Reed-Solomon (RS) encoding and cyclicredundancy check (CRC) encoding on the randomized mobile service data,encoding the RS-CRC encoded mobile service data at a coding rate of 1/N,wherein N is an integer greater than 1, mapping the mobile service dataencoded at the coding rate of 1/N into a data group and adding knowndata sequences, place holders for main service data, place holders fornon-systematic RS parity data, and place holders for moving pictureexperts group (MPEG) header data to the data group, deinterleaving thedata group, removing the place holders for the main service data and theplace holders for the non-systematic RS parity data in the deinterleaveddata group and replacing the place holders for the MPEG header data inthe deinterleaved data group with the MPEG header data having a packetidentifier (PID), thereby outputting mobile service data packets,multiplexing the mobile service data packets with main service datapackets including the main service data, randomizing, by a secondrandomizer, the multiplexed main service data packets and the MPEGheader data of the multiplexed mobile service data packets, performingsystematic RS encoding on the main service data packets from the secondrandomizer, and performing non-systematic RS encoding on the mobileservice data packets from the second randomizer, performingconvolutional byte interleaving on the systematic RS-encoded mainservice data packets and the non-systematic RS-encoded mobile servicedata packets, and trellis encoding data in the interleaved data packetsin a trellis encoding unit, wherein at least one memory included in thetrellis encoding unit is initialized at each start of the known datasequences; demodulating the received digital broadcast signal; detectingthe known data sequences from the digital broadcast signal; compensatingchannel distortion of the demodulated digital broadcast signal based onat least one of the detected known data sequences; and decoding thechannel distortion compensated digital broadcast signal.
 2. A digitalbroadcast receiver for processing digital broadcast data, the digitalbroadcast receiver comprising: a tuner for receiving a digital broadcastsignal comprising main service data, mobile service data, and known datasequences, wherein the digital broadcast signal is processed in adigital broadcast transmitter by: randomizing mobile service data in afirst randomizer, performing Reed-Solomon (RS) encoding and cyclicredundancy check (CRC) encoding on the randomized mobile service data,encoding the RS-CRC encoded mobile service data at a coding rate of 1/N,wherein N is an integer greater than 1, mapping the mobile service dataencoded at the coding rate of 1/N into a data group and adding knowndata sequences, place holders for main service data, place holders fornon-systematic RS parity data, and place holders for moving pictureexperts group (MPEG) header data to the data group, deinterleaving thedata group, removing the place holders for the main service data and theplace holders for the non-systematic RS parity data in the deinterleaveddata group and replacing the place holders for the MPEG header data inthe deinterleaved data group with the MPEG header data having a packetidentifier (PID), thereby outputting mobile service data packets,multiplexing the mobile service data packets with main service datapackets including the main service data, randomizing, by a secondrandomizer, the multiplexed main service data packets and the MPEGheader data of the multiplexed mobile service data packets, performingsystematic RS encoding on the main service data packets from the secondrandomizer, and performing non-systematic RS encoding on the mobileservice data packets from the second randomizer, performingconvolutional byte interleaving on the systematic RS-encoded mainservice data packets and the non-systematic RS-encoded mobile servicedata packets, and trellis encoding data in the interleaved data packetsin a trellis encoding unit, wherein at least one memory included in thetrellis encoding unit is initialized at each start of the known datasequences; a demodulator for demodulating the received digital broadcastsignal; a known sequence detector for detecting the known data sequencesfrom the digital broadcast signal; an equalizer for compensating channeldistortion of the demodulated digital broadcast signal based on at leastone of the detected known data sequences; and a decoder for decoding thechannel distortion compensated digital broadcast signal.
 3. A digitalbroadcast transmitter comprising: a first randomizer for randomizingmobile service data; a first encoder for performing Reed-Solomon (RS)encoding and cyclic redundancy check (CRC) encoding on the randomizedmobile service data; a second encoder for encoding the RS-CRC encodedmobile service data at a coding rate of 1/N, wherein N is an integergreater than 1; a group formatting unit for mapping the mobile servicedata encoded at the coding rate of 1/N into a data group and addingknown data sequences, place holders for main service data, place holdersfor non-systematic RS parity data, and place holders for moving pictureexperts group (MPEG) header data to the data group; a deinterleaver fordeinterleaving the data group; a packet formatter for removing the placeholders for the main service data and the place holders for thenon-systematic RS parity data in the deinterleaved data group andreplacing the place holders for the MPEG header data in thedeinterleaved data group with the MPEG header data having a packetidentifier (PID), thereby outputting mobile service data packets; afirst multiplexer for multiplexing the mobile service data packets withmain service data packets including the main service data; a secondrandomizer for randomizing the multiplexed main service data packets andthe MPEG header data of the multiplexed mobile service data packets; athird encoder for performing systematic RS encoding on the main servicedata packets from the second randomizer, and performing non-systematicRS encoding on the mobile service data packets from the secondrandomizer; and an interleaver for performing convolutional byteinterleaving on the systematic RS-encoded main service data packets andthe non-systematic RS-encoded mobile service data packets.
 4. Thedigital broadcast transmitter of claim 3, further comprising: a trellisencoding unit for trellis encoding data in the interleaved data packets,wherein at least one memory included in the trellis encoding unit isinitialized at each start of the known data sequences.
 5. The digitalbroadcast transmitter of claim 4, further comprising: a secondmultiplexer for multiplexing the trellis-encoded data with segmentsynchronization data and field synchronization data.
 6. A method ofdigital broadcast data in a digital broadcast transmitter, the methodcomprising: randomizing mobile service data in a first randomizer;performing Reed-Solomon (RS) encoding and cyclic redundancy check (CRC)encoding on the randomized mobile service data; encoding the RS-CRCencoded mobile service data at a coding rate of 1/N, wherein N is aninteger greater than 1; mapping the mobile service data encoded at thecoding rate of 1/N into a data group and adding known data sequences,place holders for main service data, place holders for non-systematic RSparity data, and place holders for moving picture experts group (MPEG)header data to the data group; deinterleaving the data group; removingthe place holders for the main service data and the place holders forthe non-systematic RS parity data in the deinterleaved data group andreplacing the place holders for the MPEG header data in thedeinterleaved data group with the MPEG header data having a packetidentifier (PID), thereby outputting mobile service data packets;multiplexing the mobile service data packets with main service datapackets including the main service data; randomizing, by a secondrandomizer, the multiplexed main service data packets and the MPEGheader data of the multiplexed mobile service data packets; performingsystematic RS encoding on the main service data packets from the secondrandomizer, and performing non-systematic RS encoding on the mobileservice data packets from the second randomizer; and performingconvolutional byte interleaving on the systematic RS-encoded mainservice data packets and the non-systematic RS-encoded mobile servicedata packets.
 7. The method of claim 6, further comprising: trellisencoding data in the interleaved data packets in a trellis encodingunit, wherein at least one memory included in the trellis encoding unitis initialized at each start of the known data sequences.
 8. The methodof claim 7, further comprising: multiplexing the trellis-encoded datawith segment synchronization data and field synchronization data.